1. Field of the Invention
The present invention relates to a semiconductor processing apparatus for performing a semiconductor process on a target substrate, such as a semiconductor wafer, and also to a method for using the apparatus. The term “semiconductor process” used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or a glass substrate used for an FPD (Flat Panel Display), e.g., an LCD (Liquid Crystal Display), by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
2. Description of the Related Art
In manufacturing semiconductor devices for constituting semiconductor integrated circuits, a target substrate, such as a semiconductor wafer (made of, e.g., silicon) is subjected to various processes, such as film formation, etching, oxidation, diffusion, reformation, annealing, and natural oxide film removal. There is a vertical film formation apparatus (of the so-called batch type), which performs a film formation process on a plurality of semiconductor wafers all together (for example, see Jpn. Pat. Appln. KOKAI Publications No. 9-246257 and No. 2002-9009). For example, a film formation process of this kind is arranged to form a thin film on semiconductor wafers, as follows.
At first, the interior of the process container of a heat processing apparatus is heated by a heater at a predetermined load temperature, and a wafer boat that holds a plurality of semiconductor wafers is loaded. Then, the interior of the process container is heated up to a predetermined process temperature, and gas inside the process container is exhausted through an exhaust port, so that the pressure inside the process container is decreased to a predetermined pressure.
Then, while the interior of the process container is kept at the predetermined temperature and pressure (kept exhausted), a film formation gas is supplied through a process gas feed line into the process container. For example, in the case of CVD, when a film formation gas is supplied into a process container, the film formation gas causes a thermal reaction and thereby produces reaction products. The reaction products are deposited on the surface of each semiconductor wafer, and form a thin film on the surface of the semiconductor wafer.
Quartz component members, such as the process container, thermally insulating cylinder, and wafer boat, are made from high quality quartz material with high purity and few impurities to prevent wafers from suffering metal contamination. However, a trace amount of metal is inevitably contained in the quartz material from the beginning, or a trace amount of metal is inevitably mixed, e.g., as an oxide in the quartz material during a process step, such as welding, of manufacturing thereof.
Accordingly, for example, when semiconductor wafers are processed within a reduction atmosphere, a metal oxide contained in quartz material as described above is subjected to a deoxidizing reaction. Consequently, a metal is precipitated on the surface of the quartz material, and may bring about metal contamination on the wafers. Particularly, as metal contamination, copper contamination due to copper oxide is prominent.
Conventionally, as a method for preventing such metal contamination, the following methods are known. Jpn. Pat. Appln. KOKAI Publication No. 5-109640 discloses a cleaning process in which hydrogen gas, which has a gettering function for removing metal contaminants, is supplied into a process container to remove metal contaminants. Jpn. Pat. Appln. KOKAI Publication No. 2002-313787 discloses a cleaning process in which a halogen compound, such as HCl gas, is supplied into a process container to transform metals into chlorides having high vapor pressures, so as to remove metal contaminants by sublimation.
A cleaning process of this kind is performed when a new member made of quartz material, such as a wafer boat or thermally insulating cylinder, is installed, because metal contaminants may be present on the surface of this member. Further, a cleaning process of this kind is regularly or irregularly performed when a film formation process is repeated a predetermined number of times, because metal contaminants contained in quartz material may be diffused toward the surface every time the heat process is performed.